Transparent textures broken on ETQW

[Kontrabant]

While investigating #370, it seems that transparent textures in-game are broken when running via sdl12-compat (on top of the latest sdl2-compat and SDL3). Rendering is correct when using the native (modified) SDL 1.2 shared library the game ships with.

To reproduce (borrowed from #370):

ETQW Demo:

https://cdn.splashdamage.com/downloads/games/etqw/ETQW-demo2-client-full.r1.x86.run

After installing the demo, the game ships with a custom SDL 1.2 build, which needs to be manually overridden. On my Fedora 42 system:

• mv libSDL-1.2.id.so.0 libSDL-1.2.id.so.0.bak
• ln -s /usr/lib/libSDL-1.2.so.0 <install path>/libSDL-1.2.id.so.0
• SDL_VIDEODRIVER=x11 ./etqw-rthread

Note: The game uses Nvidia's cg to compile shaders, which needs GLX, so Wayland is not expected to work. This is not currently detected, so manually specifying X11 is necessary if running via sdl2-compat.

X11:

Transparent textures are broken, and the logs are filled with messages that look like shader compilation failures along the lines of:

WARNING: GL_PROGRAM_ERROR_STRING_ARB: 
GL_PROGRAM_ERROR_POSITION_ARB < 0 with error
WARNING: idDeclLocal::ParseLocal Failed to Parse decl 'trivialrgb' in file 'renderprogs/trivial.rprog' line 0
WARNING: sdDeclRenderProgram::ResolveReferences : Reference shader of type 1 is defaulted in 'trivialrgbwithtexturematrix'
WARNING: idDeclLocal::ParseLocal Failed to Parse decl 'trivialrgbwithtexturematrix' in file 'renderprogs/trivial.rprog' line 0
WARNING: file materials/shaderdemo.mtr: wipe2material, line 0: Unable to parse render program 'trivialRGBWithTextureMatrix'
WARNING: idDeclLocal::ParseLocal Failed to Parse decl 'wipe2material' in file 'materials/shaderdemo.mtr' line 0

This is on the proprietary NVIDIA 580.82.09 driver. I attempted to test with Zink, but it hangs on startup. Reverting to the real SDL 1.2 build that ships with the game fixes it, but mouse grabbing is broken.

[smcv]

This is on the proprietary NVIDIA 580.82.09 driver

On #370, @rea987 says the same thing happens on AMD/Mesa.

[rea987]

@Kontrabant, Could you please try libXi.i686 on Fedora to see if that fixes the issue?

#370 (comment)
#370 (comment)

[Kontrabant]

It's still broken, which was expected as libXi doesn't have anything to do with rendering, and the build I was initially testing with didn't have it disabled.

[icculus]

Just spitballing here, but if it's the shader compiler complaining and real SDL 1.2 otherwise works on the same setup, surely this must mean we're getting a different GL profile or GL version when creating a context via sdl12-compat, so you get different rules about what qualifies as a valid shader...?